Field of Invention
This invention relates to drive systems for agricultural vehicles such as harvesters.
Description of Related Art
Harvesters are large and heavy and therefore difficult to turn. A conventional harvester includes powered non-steering front wheels and non-powered rear steering wheels, although some harvesters provide power to the rear wheels as well. Much of the harvester's weight is supported by the powered non-steering front wheels, which resist turning. Thus, the rear steering wheels often can't sufficiently control the harvester trajectory. A harvester drive system may include various components for propulsion traction assistance such as an open locking differential, variable speed or variable displacement pumps and motors, and final drive gearboxes, but these components and the powered front non-steering wheels do not actively help steer the vehicle. A process called torque vectoring, in which a turning torque is applied to the harvester via the front wheels, may be used to assist the harvester in turning. However, this process requires speeding up or slowing down one of the front wheels, which in turn speeds up or slows down the harvester when turning. Other agricultural vehicles experience these same problems.